1. Technical Field
Aspects of the present invention relate to optical transceiver modules, and more particularly to a wideband impedance matching circuit design that simultaneously provides a high bandwidth signal path from a laser diode driver to a laser diode and shields against parasitic effects from a DC current supply of the laser diode.
2. Description of the Related Art
Laser diodes operating in high data rate optical transceivers or transmitters need a wideband high-frequency (AC or RF) connection to the laser diode driver circuit which sends the data to be transmitted, and a DC current supply connection to the laser diode for establishing the operating point.
Some optical modules establish the operating point through RF lines, which require higher biasing voltage and produce higher power dissipation.
For the optical modules where DC and RF are connected using different circuits the following considerations may apply. The RF lines demand a careful design over the bandwidth of the signal to be transmitted (here up to 15 GHz for a 10 Gb/s application). The DC connection is less sensitive, but presents additional challenges for the RF design since it must be decoupled for the entire frequency range (e.g., above 10 MHz or in general 1×10−4 of the data rate).
This decoupling is done by so-called RF chokes which are commercially available. RF chokes represent a low impedance path for DC currents but a high impedance path for RF signals. However, parasitic electromagnetic effects (capacitive coupling and inductive voltage drops) associated with the placement and design of RF chokes can disable the decoupling and hence degrade signal transmission to the laser diode.